[sf3543]

I have never used the Silicone Baffle material before, but am installing it on my RV8.
My question to the group is: Will the silicon baffle material eventually take a set to a more bent over state, like the reinforced materials did?
My installation looks great and provides a good seal once the cowling is on, but the rear pieces stick straight up and it is difficult to get the cowl on. I have 1 1/2 " of material above the baffle edges.
Any of your experiences would be appreciated. If it remains this difficult, I'll go back to the material supplied by VAN's, but thought I'd try this since I like the blue color.

 

[kevinh]

I helped a friend with his Glastar. He was having a devil of a time getting a good seal with the blue stuff on his (100ish hour) airplane. He switched to the van's black stuff and the problem was solved - good tight seal in just a few hours.

YMMV ;-)

 

[osxuser]

It should bend over with time, but not the extent that the black stuff does. On the other hand, it will last longer.

 

[gmcjetpilot]

look at other projects

My advice is surface the web for builder sites to see how to do the seals, this is almost more important than what material to use. However the pure silicone material is better than vans black rubber fiber material provided. The silicone is not cheap but it will last and not take a set.

A good list of builders can be found on Van's web site under links. Also don't just look at the model you have. All RV's have the same baffle seal set up. Most builders have a engine/firewal-fwd/finish section on their site. Look at as many as you can. Even the Harmon Rockets and F-1 Rocket web sites have great pictures of how to do soft baffle seals.

Some builders baffle seals are a work of art. Bad seals will be the gift that keeps taking. Leaks are going to increase CHT and the air passing thru the cowl inlet and leaking direct to the lower portion of the cowl reduces the pressure differntial from top to bottom. That P diff is what cools the cowl. Bottom line air leaking thru the system is air not doing cooling and causing drag (ie lower speed).

For what it is worth, take great care in installation because this affects engine cooling and speed (leaks are cooling drag)**.


I got rid of the soft seals altogether for a hard plenum cover. There is no doubt that it is leak free**, supports the top of the baffle sides reducing cracking and most important you do not have to deal with soft seals. Also not relying on the top of the cowl to hold the internal pressure reduces the load on the piano hinges and maintenance. The down side is once you take the cowl off you do not have direct access to the top of the engine unless you remove the top cover of the plenum. Maintenance access holes for the top plugs will reduce this burden. Also I am using a Custom made cowl that looks like a Sam James/Holy Cowl, aka round inlets. I only mention it because many have used the "dog-house approach both with Van's stock cowl and round inlet style. You may want to consider? Again check builder sites for ideas.

George.


**NASA sponsored research by Mississippi Stat e in the late 70's, early 80's showed reducing the leaks in the baffle (by making is a solid sealed box) reduced cooling drag. Also it is easier to make a perfect seal between the cowl inlets (round) and the plenum with ducts, which further reduces leaks and promotes smooth airflow into the plenum.